Submerged oil storage tank

ABSTRACT

A submerged liquid storage system comprises a foundation base resting on the ocean floor and including a ballastable platform having integrally mounted thereon an upwardly extending tapering hollow shaft interlocking with a tank enclosure comprising an assembly of interconnecting and intercommunicating horizontal and sloping tubular struts braced against said shaft, covered by a flexible sheet of elastomer material serving as an sealed tank wall open on the bottom to sea and forming with the said tubular struts and hollow shaft a liquid storing tank, with the said tank being protected from marine environs by an outer timber envelope.

United States Patent 1 Malkiel SUBMERGED OIL STORAGE TANK [76] Inventor: Arick S. Malkiel, 94-09 68th Ave.,

Forest Hills, NY. 11375 [22] Filed: Sept. 29, 1972 [21] Appl. No.: 293,400

[52] US. Cl. 61/46.5, 114/.5 T [51] Int. Cl. E02b 17/00, B65d 89/10 [58] Field of Search..... 61/.5, 46, 46.5, 69 R; 114/.5 T

[56] References Cited UNITED STATES PATENTS 3,712,068 1/1973 Liautaud 61/46.5 3,686,875 8/1972 Morgan.. 61/46 3,643,447 2/1972 Pogonowski 61/46 3,429,128 2/1969 Stafford et a1. 61/46 3,113,699 12/1963 Crawford et a1 61/46.5 2,977,018 3/1961 Frye 6 l/.5 2,487,786 ll/l949 Bogle 6l/.5

[4 1 Apr. 16, 1974 Primary Examiner-Louis K. Rimrodt Assistant Examiner-Alex Grosz Attorney, Agent, or FirmHugo E. Weisberger [5 7] ABSTRACT A submerged liquid storage system comprises a foundation base resting on the ocean floor and including a ballastable platform having integrally mounted thereon an upwardly extending tapering hollow shaft interlocking with a tank enclosure comprising an assembly of interconnecting and intercommunicating horizontal and sloping tubular struts braced against said shaft, covered by a flexible sheet of elastomer material serving as an sealed tank wall open on the bottom to sea and forming with the said tubular struts and hollow shaft a liquid storing tank, with the said tank being protected from marine environs by an outer timber envelope.

13 Claims, 10 Drawing Figures SHEET 2 or a ATENTEB APR 1 6 1974 PATENTEDAFR 16 I974 SHEET 3 OF 4 FIG. 5A

FIG. 7

SUBMERGED on. STORAGE TANK BACKGROUND OF THE INVENTION prominent factor in the economics of petroleum production and distribution. I

In general, floating storage facilities, which usually comprise large vessels having capacities of 70,000 to 100,000 deadweight tons, represent an initial investment about one-third less than that for onshore storage facilities, which require platforms and feeder pipelines. However, since floating storage facilities offer a potential pollution hazard, and possible loss due to weather conditions, intensive efforts are under way in the oil production industry to replace these with submerged storageunits planted on the ocean floor.

In the design of submerged oil storage tanks and the like, the prevailing forces to which the tank may be subjected must be taken into account. These include:

- (1) Negative, counter-gravitational forces or buoy ancy. These forces are variable in magnitude and are a function of the specific gravity of the stored oil and of the level of oil maintained in the tank. (2) Forces generated by currents upon the submerged tank. These forces are of a sustained nature and of a magnitude more or less variable, and are inversely proportional to the depth below the free water level. (3) Wind generated forces-waves. Wind generated waves are characterized by sinuous or oscillatory wave form, in which each wave particle isfsubject ed toa compound orbital and longitudinal displacement, with wave period, wave length, and propagationbeing inter-related. The successive shifting of the peaks and valleys ofthe waves forms a wave train which travels over the free water surface, with a velocity the same as the orbital velocity of the wave particles.

A type of submerged offshore storage tank described in the prior art is that shown in US. Pat. No. 3,429,128, which utilizes an open-bottom shell shaped like an inverted funnel, and provided with a centrally located cylindrical bottle to assist in submergence, the lower edge of the tank being anchored directly to the ocean floor, to which it is lowered after previous assembly on shore, piles being used to sustain the tank structure against buoyancy, lateral and surge wave forces. In another known type of storage facility, intended for off-shore use, and described in Engineering News Record, May 18, 1972, page 42, a concrete oil storage tank is partly fabricated on shore, towed to location and sunk, and the walls are completed by slip-forming to a point above the surface. A perforated outer wall acts as a breakwater to absorb wave forces.

SUMMARY OF- THE INVENTION In accordance with the present invention there is provided a novel submerged oil tank system having two principal components:

1. a foundation base such as a steel and concrete encased platform which is prefabricated on shore, launched and towed to location and there sunk, with subsequent ballasting as necessary. There is mounted in the center portion of the foundation base, so as to be integral therewith, an upwardly extending tapering hollow shaft or column, which is submerged below the surface of the water and which, subsequently, serves as an interlock for the-other principal component, which is (2) a tank enclosure, comprising an assembly having a generally frusto-conical shape, adapted to be mounted withits upper end to be interlocked with the central shaft, thereby forming a structural entity with the foundation base shaft at its upper end, and with its lower edge resting on the foundation base. The tank enclosure includes two series of interconnecting hollow tubular struts, one arranged horizontally, and the other sloping upwardly, the interior of the struts providing means for ballasting with water to-accomplish the sinking of the tank enclosure, and ultimately providing means for additional storage of oil. The strut construction is surrounded by a tank envelope which is made up of one or more layers of a web of a flexible material, and which is protected against sea environs and outside forces by an outer layer or envelope of timbers spaced apart to provide slots to dissipate energy from wave forces. The envelope is open to sea along the juncture with the foundation base and at the upper end sealed with a dome-type enclosure. The inner envelope is aptly made of panels of material having appropriate elasticity to become deformed to a perceptible degree under the applied pressures. The panels, under induced pressures, will deform (bulge) to an extent to cause volume displacement of the oil and/or water contained in the tank hold. Said volume displacement will effect an energy diffraction (dash-pot phenomena) attenuating the impact of the waves pressure and drag impulses imposed on the envelope.

Thus-the present invention by structural concept and configuration provides a submerged oil'storage tank which affords a minimum of exposure to prevailing undersea forces and which represents an optimum use of structural materials.

Virtually all prior art underwater tank systems rely on built-up very heavy structures or on anchorage on or into the ocean floor. The system of the present invention is supported from a weighted foundation or pad adequate to' withstand high seas as encounterd in open waters.

The two component system of the present invention enables the foundation component to be towed to site, sunk and ballasted as required, to guide, receive, and lock-in a buoyant tank enclosure fabricated from comparatively light weight parts and capable of being assembled in such manner'as to provide sufficient buoyancy when assembled and in readiness to be guided to the foundation base.

The envelope construction employed in the invention provides the advantages of light weight and sufficient strength to resist inner buoyancy forces, with the outer timber envelope giving protection against high intensity wave and surge forces and serving as a barrier against the marine environment. The invention provides for the total recovery of the structure, or the tank only for inspection and maintenance purposes and its subsequent replacement onto the submerged foundation base.

- BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic cross-sectional view of a tank foundation base, installed on the ocean floor, according to the invention;

FIG. 2 is a diagrammatic cross-sectional view of a tank enclosure, for mounting on the-foundation base of FIG. 1, according to the invention;

FIG. 3 is a diagrammatic cross-sectional view taken on line 33 of FIG. 2;

FIG. 4 is a diagrammatic cross-sectional view of the FIG. 1 base and FIG. 2 enclosure in assembly;

FIG. 5 is a side view showing the means of attaching the tank envelope and protecting outer timbers to the enclosure frame;

FIG. 5A is a plan view taken on the line 5A5A of FIG. 5;

FIG. 6 is a sectional view showing the mode of interconnection between the sloping strut and the horizontal strut systems;

FIG. 6A is an elevational view taken on the line 6A6A of FIG. 6. I

FIG. 7 illustrates one means of fastening the tank envelope to the upper end of the foundation column.

FIG. 8 illustrates one means of seating the tank enclosure on the foundation base.

DETAILED DESCRIPTION OF THE INVENTION The invention will be illustrated by a presently preferred embodiment which, referring to FIG. 1, comprises a foundation base 10, which is laid on, and at least partially imbedded in the ocean floor F. The foundation base 10 comprises a hollow shell 12, preferably circular in configuration, which may be constituted of structural steel plating. The shell includes a bottom wall 13 which rests on the ocean floor and which is provided with centrally located flooding vents 14, the purpose of which will be explained hereafter.

The bottom wall 13 of the steel shell rests on the ocean floor, preferably imbedded therein slightly below the general contour. At the periphery of the shell there is provided a downwardly projecting cutting edge portion 15 which forms the lower end of peripheral wall 16. The foundation base is partially lined with concrete l7 defining the extent of space ,18 for receiving ballast material. The roof 19 of the foundation base is in the form of an annular flat plate having a plurality of air escape vents 20, which permit displacement of contained air when ballast is introduced into the shell.

Integral with the foundation base shell and forming a part thereof is a central hollow shaft 21, having its lower portion 22 in the shape of a truncated cone, which is connected to the upper plate 19 of the base shell at juncture 25 by welding or other suitable means. The hollow shaft 21 and 22, the roof 19, peripheral walls 16, and bottom wall 13, are interlaced with struts 23 and 24 to comprise an integrated space structure capable of resisting forces encountered during towing, sinking, ballasting operations, and subsequently as the tank foundation base. The central shaft portion 22 is provided with a plurality of bulkheads 26 for communication between central shaft and tank hold. The

upper end of conical portion 22 is connected during the installation period, by a joint 27, with a vertical upwardly extending cylindrical portion 28 having cap 29, including an inlet 30, at its upper end.

The inlet opening 30 serves'as a means of introducing supporting services such as power, air, water and ballast, as required for the various assembly and erection stages. 4

The foundation base shell 12 includes, at the inner periphery of the upper plate 19, an annular inclined segment 23 which supports a ring shaped plate 34 which constitutes a bearing and guide for the cone shaped tank enclosure which subsequently is lowered onto the foundation base, as hereinafter more fully explained. The struts 23 and 24 are arranged in a space truss-like manner and do not interfere with flow of liquid or water, sand and gravel mixture introduced under pressures.

The cylindrical portion 28 is provided with a plurality of vents 14a and in the conical portion 22 with vents 14b, located just above the ballast filling level F, as indicated in FIG. 1, the purpose of which is explained hereinafter.

In accordance with the invention, the foundation base component is advantageously constructed on shore and the base 10 and shaft 21 are braced by a plurality of guys 32. After assembly, with bulkheads 26 and vents 14, 20, 14a and 14b closed airtight, it is launched and towed to the desired location. At site location the foundation base is lowered onto the ocean floor by introducing compressed air through shaft inlet 30 and the simultaneous opening of flooding vents 14 installed in the base lower plating l3. Thereafter air pressure is removed, vents 14 are closed, and vents 20 and 14b are opened and the foundation base and shaft are flooded. Thereafter the foundation base is ballasted to level F by introducing suitable gravel or concrete materials from a supply vessel through shaft inlet 30, which material displaces contained water through the several vents provided therefor and to fill wholly the base 10. The knife edgeportion 15 is dug into the ocean floor and will prevent drifting. Once the foudation base is in place, the several guy wires 32 are-disconnected to permit subsequent lowering of the tank enclosure portion onto the base.

The foundation base structure is completely submerged and its upper portion is below the water surface W. However, for ballast filling purposes, the tower can be temporarily extended to the water surface, and the extension portion subsequently removed. By way of illustration, and not of limitation, the dimensions of the base may be, for example, 180 feet in diameter, the lower platform portion 8 to 10 feet deep and the tower portion about feet in height. The steel plate may be of approximately half inch thickness.

The structure and functioning of the tank enclosure component of the oil storage system of the invention may be better understood by referring to FIGS. 2 and 3 of the drawings which illustrate the tank enclosure portion in assembled form ready to be lowered onto the foundation base. As shown in FIG. 2, the tank enclosure comprises a frame assembly 40 and tank envelope 50. The frame assembly is composed of sets of hollow tubular struts, including a system of a plurality of vertical (sloping) members 41 arranged in the form of a cone which is joined and interconnects with a horizontal system of a plurality of tubular struts 42, arranged in a concentric ring-like polygon pattern as shown in FIG. 3. Each of the sloping tubular struts 41 terminates at its lower end in a cap or foot 54 which rests against the inclined segment 33 and bearing plate 34 of the foundation base, thereby providing a peripheral support and guide for the lower portion of tubular system as shown in greater detail in FIG. 8.

Referring to FIGS. 2 and 3, the tank envelope 50 is provided at its upper portion with a dome-type enclosure 43 which'has an inlet opening 44 for appropriate services in an upper dome portion 45 surrounded by a peripheral wall 46 terminating at its lower end in an inwardly extending annular ring 47. The dome member 43 serves both as an airlock and as an extension of the sealed envelope 50 of the enclosure 40 as explained hereafter. At each intersection the sloping and the horizontalstruts 41' and 42 are bracedby radially disposed pre-tensioned members 49 arranged in groups with each group extending from acentrally disposed ring girder 51 to a specially designed connection 48 with the respective intersecting struts as shown in FIG. 6. The

members .49 slope slightly toward the center shaft owing to their dead weight which inturn is in equilibrium with the pre-tensionedforce in the member. The

diameter of each ring girder 51 is such that it will suitably conform with, appropriate clearance to the dimension of the central shaft 21 at the elevation of said ring girder, when the tank envelope is in place on the central shaft, as shown schematically in FIG. 4.

In general, a clearance of an estimated 2 feet all around should be maintained to allow for lateral displacement of the tank enclosure under one-sided forces. The ring girder 51,.radial struts 42, and pretensioned members 49 comprise a rigid membrane in each of the respectivehorizontal planes, capable of sustaining one-sided loads in the same fashion as a vehiclewheel having an outer flexible rim which is interconnected to the central bearing portion via pre-tensioned spokes. However, in a three-dimensional structure as contemplated by the invention, each of the thus created horizontal membranes will not be stable unless along the envelope of the formed cone a bracing system is introduced. Sucha bracing system is provided in the present invention by sets of bracing cables 59 which are strung between alternate sloped struts 41, as shown in FIG. 3.

Referring to FIG. 5, there is illustrated the means of attaching the elastomeric tank envelope and the outer protecting timbers, to the horizontal struts of the tank enclosure'frame at any given point. Surrounding the frame structure 40, tank envelope 50 is made up of individual elastomeric air tight envelope panels 60 which taken together wrap around the sloping struts so as to form a near conical tank wall, of which the shaft 21 and all struts 41 and 42 will become part after appropriate interconnecting bulkheads and vents will-have been opened. The envelope panels 60 may be made of any suitable oil resistant rubber or plastic material, such as, for example, neoprene, and which serves to form the outer wall of the oil storage tank. Surrounding the elastomeric envelope panels 60, is a protective structure made up of a series of timber members 61 spaced with appropriate clearance in between to accomplish energy dissipation of on-rushing wave forces by introducing turbulence.

The timbers are attached to the horizontal tubular members 42 by means of a continuous steel mounting assembly 62, one end of which is welded to the tubular strut 42 at point 65 and the other end of which receives a fastener 63 such as a bolt, and nut combination, which is secured to the respective timber 61 via a hole adapted to receive same. The mounting assembly 62 includes a supporting plate 64 to which the elastomeric envelope paneling 60 is attached by suitable means at point 66 so as to form a seal.

The alignment of the panels follows that of the horizontal struts 42, and the panels will typically have approximately an 8 to 10 foot span.

Further, as shown in FIG. 5, the pre-tensioned member 49 is attached to each of a pair of contiguous horizontal struts 42 by means of a set of two plates 74, one of which is depicted in FIG. 5. The arrangement of the plates 72 is shown in greater detail in FIG. 6. The pair of plates 72 form an anchorage assembly for pretensioned member or cable 49 via an anchor bolt arrangement 78.

FIG. 5A illustrates the means employed to obtain continuity of the individual panels of the envelope structure, and the way in which adjacent sets of panels 60 are joined by interconnecting panel 60a, which is attached to supporting plates 64a forming an extension of supporting plates 64 which are attached to mounting assembly 62, as described in connection with FIG. 5.

In FIG. 6, there is shown, in sectional plan view, the interconnection system between a hollow sloping strut 41 and a pair of horizontal tubular struts 42, at the point where they intersect. This system permits the free flow of liquids through and between the respective struts. This enables the structure system to be employed initially as a means for ballasting. the tank enclosure with water to enable it to be sunk into position on the foundation base, and ultimately provides as a system for additional storage of. oil.

Each horizontal strut 42 terminates in a flange 70 having a centrally located opening 71. Attached to the outer surface of each flange 70 is a flat plate 72, having an opening 73 which is in registry with opening 71 of the flange, to permit movement of liquid therethrough. The plates 72 are converged inwardly to form an angle corresponding to that of the polygonal horizontal strut layer as shown in FIG. 2, at that point, thus serving to hold the contiguous horizontal struts 42 in spaced relationship, each' plate being perpendicular to the axis of the strut 42 and the flange 70 to which it is attached. Said flange 70 is attached to the respective horizontal tubes 42, by welding or other suitable means.

As mentioned, each of plates 72 has a central opening 73 which is in registry with the central opening 71 of the tube flange thereby permitting free flow of liquid from in andout of the respective tubular members.

As shown in FIG. 6A, the plates 72 are welded to a pair of parallel cross plates 74 which traverse slots 74a cut in sloped tubular member 41 and are welded in place.

Cross plates 74 and their corresponding slots 74a are aligned so as to be parallel to the axis of strut 41.

Between the pair of plates 72 are installed spaced apart a pair of stay plates 75 which serve as part of the anchorage assembly for the pre-tensioned members 49 which bear thereupon through cross plates 76 and pretensioning nut 76a, said pre-tensioned members 49 terminating inbound in the respective rings 51 serving to maintain the configuration of the tank envelope as illustrated in FIG. 2.

As shown in FIG. 6, the plates 74 are arranged to pass through the sloping tubular strut 41, thereby forming a joint assembly for the tubes 41 and 42 and tie members 49 and are being arranged to provide strut 41 with a pair of openings 77 at a point opposite the opening 71 of the horizontal tube 42, thereby permitting free passage of liquid between said horizontal and sloping tubular members.

There is shown in greater detail in FIG. 7 the means of fastening the dome type enclosure 43 to the tank envelope 50 and of connecting the upper ends of the sloping members 41 to the upper portion 28 of the foundation column. The upper cylindrical portion 28 of the foundation shaft has an annular reinforcement member 80 which serves to receive the bearing thrust of the plurality of the sloping tubes 41 by means of an attached bearing plate 82 and connecting plate 83. Bearing plate 82 forms an integral part of the strut as assembled and only connecting plate 83 needs to be fitted and welded in place. When the tubular framework is lowered into place the connecting plate 83 welded in place serves to interlock the tank enclosure 40 to the foundation base.

This interlocking of the sloped struts 41 into the center column 28 of the foundation base is illustrated in FIG. 7, in which the uppermost envelope mounting assembly 62a is shown modified to an extent that the plate 64a is reinforced with ribs 83a and 83b to accommodate the weight of the dome type enclosure 43 and to facilite an airtight welded seal 83c between tank envelope 50 and said dome type enclosure.v

FIG. 8 shows one means of seating the lower. end of the enclosure 40 through sloping members 41 to the annular inclined segment 33 of the foundation base (see FIG. 1). This fastening means comprises a ring steel plate 34 embedded into the-foundation base inclined segment 33 and having guide plates 86 associated therewith to facilitate the seating of the inclined rubular members 41 which terminate in a bearing plate 54. The upper guide plate should present a vertical face to facilitate seating of the tank enclosure onto the foundation base. As illustrated in FIG. 8, the lowermost envelope mounting assembly 62b is modified to an extent that the plate 64b is extended to connect envelope panels 60b and timber enclosure 61b on the upper side only, thus terminating the tank envelope 50 there, and permitting free communication between sea and tank hold.

The uppermost ring assembly struts 42a are provided at their upper ends with vents 53 as shown in FIG. 4 and the sloped struts 41 are provided, at a point below the lowest ring assembly, with vents 55, as shown in FIG. 4. The system of vents 14a, 14b, bulkheads 26 and vents 53 and 55 facilitates the flow of air, water, or oil between the tank hold, the foundation base center shaft, and the two-way hollow struts of the tank enclosure. As shown in FIGS. 2 and 8, the tank envelope 50 terminates at the lowest ring assembly 42b permitting communication between the water body and the tank hold.

The method of installing the submerged liquid storage system at a given underwater site comprises: erecting the foundation base, including the hollow shaft, on shore; launching the foundation base into a body of water and towing the base to a point above the chosen site for the storage system; introducing air under pressure into the hollow shaft in order to compensate flooding of the base through opening flooding vents and to maintain buoyancy of the foundation base assembly during ensuing base submergence onto the site. The foundation base is filled or ballasted as required.

The assembly of the enclosure frame and envelope at the selected site, in accordance with the invention, involves a novel principle of successive assembly with simultaneous maintenance of buoyancy. The application of this principle in the erection of the tank enclosure at the site involves the following operational steps: The vent 55 (see FIG. 2) being closed, the initial part of the strut assembly, comprising the lowest portion of struts 41 interconnected with the two lowest horizontal struts 42 and tied back to the ring girder 51, will present a three-dimensional stable and buoyant segment of the tank enclosure upon which successive extensions of the sloping struts 41 can be added with the horizontal ring components being simultaneously assembled in place. The buoyancy of the assembled lower portion as described, will facilitate the assembly of successive additional parts above water, thus increasing the buoyancy of the already completed parts of the enclosure and offsetting the progressive increase in weight of the portion previously assembled.

In this manner there may also be completed the assembly of the tank enclosure and the elastomer envelope, including the timber envelope, which also contribute to the buoyancy, and finally there is added the dome-type enclosure 43. At this point the completed enclosure will still be buoyant and will float with its major portion of struts and envelopes submerged, but with the dome-type enclosure portion projecting above the water surface. Thereafter, the seal between the dome-type enclosure 43 and the upper portion of the elastomer envelope 60 is effected. After this completion, air pressure may be introduced with simultaneous opening of vents 55, so that the hollow tubular struts of the enclosure may be floated, with any loss of buoyancy being compensated by the introduction of compressed air. By appropriate manipulation and adjustment of the air pressure and the vents, and utilizing the guidance provided by the central shaft of the foundation base, the tank assembly is lowered onto the foundation base so that the upper portion of the enclosure interlocks with the upper portion 28 of the foundation shaft, as shown in FIG. 7, and the lower ends 54 of the sloping struts are seated against the annular steel plate 34 embedded in the foundation base.

Under buoyant forces or surge, the conical tank structure will tend to rise, and by interlocking it with the central shaft; all the buoyant and uplift forces will be negated by the deadweight of the foundation base. This implies that the sloped tubular struts will be subjected to compression and the center shaft to tension, by the ballasted foundation base. One of the main features and advantages of the invention is that the preassembled foundation base less ballasting is buoyant without introducing compressed air. The configuration of the base, which is airtight if all the vents are closed, with the center shaft being a part of the foundation base buoyant volume, imparts exceptionally favorable characteristics to the center of gravity of the mass, and consequently high seas will be unable to upset the equilibrium of the base. Only after the foundation base is centered over the site where it is to be sunk, does flooding and the introduction of compressed air take place to facilitate the sinking of the foundation base. Manipulation of the vents can be made by remote control, or by divers.

In order to transport the tank enclosure assembly to another location, the oil is'removed from the tank via the airlock chamber 43, thus filling tank with water. Since the oil is lighter than the water, oil will be expelled under pressure differential and its volume will be taken by the water. Thus, after oil is removed from the tank, the tank is fully of water, only then, the compressed air will be introduced to expel the water to an extent as required to raise the tank enclosure but not prior to disconnecting the interlock between the sloped struts and foundation'base center shaft. The water is then displaced by the introduction ofcompressed air to an extent that additional air pressure will then raise the tank enclosure to desired level for inspection, servicing, removal to a new location, or for dismantling. Similarily, the foundation structure can be rendered buoyant by purging the gravel ballast out of the foundation base and by the introduction of air under pressure into the central shaft 21, thereby floated and towed to a new location.

While the present invention has been described with reference to the specific embodiment shown in the drawings, it will be understood that variations may be made in the shape and configuration of various portions of the system, including the overall shape of the tank. Thus, the foundation base need not be circular but may be square or rectangular as particular needs dictate it. Furthermore, the outer portion of the tank enclosure need not be conical but may have the configuration of any desired surface of revolution such as'of a paraboloid, hyperboloid, ellipsoid, or of a polygon comprising two or a plurality of sides.

The mode of operation of the submerged oil storage system according to the invention is as follows:

After the interlocking of the tank enclosures and envelope into the foundation is completed and the vents and bulkheads 55, 26, 14a, 14b and 53 are open to effect free flow between tank hold and the vertical and horizontal enclosure hollow strutsand foundation center shaft, the: tank is operational for storing of oil. Appropriate oil pipes can then be connected to the tank via the inlet opening 44 at the top of the dome-type enclosure 43; the'pipi'ng may terminate either in a specially devised oil handling'platform above sea level and/or directly'by connecting to tankers.

Due to the difference in specific gravities of oil and water, the oil will have to be subjected to a pressure greater than the differential in head between stored oil and the displaced water. As pumping under pressureof the oil continues, the water contained in the tank hold will be purged through the slot openings between horizontal struts 42b and foundation base annular segment 33. Sincethe oil is lighter than the water there will be a distinct interface above which the oil will be present and below which is the body of water. As the interface of lowered 'to a specific level beyond which more pumped oil may escape from the tank, the pumping of oil will have to be discontinued. The level of the inter face may-be controlled at all times by appropriate electronic instrumentation'to safeguard oil spillage from the tank.

As mentioned before, by maintaining the vents and bulkheads open for free flow within the tank hold, and hollow struts and foundation center shaft, the interface between oil and water will be maintained at the same level across-all the components intended for storing of oil.

The removal of oil follows a reverse procedure, i.e. by opening the appropriate valves at the upper end of the oil pipes will effect the oil to raise from the tank hold under the differential pressure head created by the heavier water entering the tank through the slots at the bottom of the tank. The removal of oil may be of course accelerated by introducing appropriate suction pumps at the oil pipe upper terminal points.

What is claimed is:

l. A submerged liquid storage system adapted for offshore use, comprising in combination:

a. a foundation base adapted to be positioned on the floor underlying a body of water, comprising a ballastable hollow platform having integrally mounted in the central portion thereof an upwardly extending tapering hollow shaft in communication with said hollow platform adapted to support and interlock therewith a tank enclosure at the upper portion of said shaft;

b. a rigid tank enclosure framework removably mounted on the exterior of said shaft, comprising an assembly of a plurality of interconnecting and communicating horizontal and upwardly sloping rigid tubular struts, said sloping-struts diverging toward the lower end of the assembly to provide the configuration of a surface of revolution;

c. a plurality of individual panels of a web of flexible elastomeric material forming an envelope surrounding the exterior of said rigid framework and mounted thereon to provide an outer tank wall, and defining, in combination with the outer surface of said shaft, a hollow storage space;

d. means located on the upper surface of said foundation base for separably supporting the lower end of said tank enclosure framework; and

e. means for introducing or removing liquid located at the upper portion of said tank enclosure and communicating with the storage space formed by said enclosure and the shaft.

2. The storage system of claim 1 in which said foundation base shaft includes a frusto conical lower portion merging into a cylindrical upper portion, said lower portion communicating with the interior of said platform.

3. The storage system of claim 1 in which said foundation base includes a peripheral downwardly extending cutting edge member adapted to penetrate said floor when the foundation base is ballasted and thereby anchor the storage system and prevent drifting.

4. The storage system of claim 1 in which said platform includes a peripheral inclined annular member adapted to support the lower ends of said sloping tubular struts of said tank enclosure seated thereon.

5. The storage system of claim 1 in which said tank enclosure and its upwardly sloping supporting strut system is generally conical in configuration.

6. The storage system of claim 1 in which said struts are braced at their points of intersection by a plurality of radially disposed bracing members extending inwardly and connected to an annular girder member engaging the outer surface of said shaft, the respective girder members for each strut set having a diameter corresponding to the configuration of shaft at the level of the set.

7. The storage system of claim 1 in which said tank enclosure includes at its upper end a hollow vessel communicating with the interior of the enclosure and having inlet or discharge means in its roof for receiving or removing materials, and being removably connected with the upper end of said strut framework to form an airlock and a seal with the upper end of said envelope.

8. The storage system of claim 1 in which the upper ends of said sloping tubular struts are fastened to the upper portion of said shaft thereby interlocking said tank enclosure to the foundation base.

9. The storage system of claim 1 in which said tank enclosure further includes an outer protective structure located exteriorly of said elastomeric material and fastened to said framework comprising a plurality of spaced buffer members capable of resisting and reducing wave forces.

10. The storage system of claim 1 in which said sloping tubular struts are provided with vent means located adjacent the upper and lower end of the strut to permit passage of air or liquid therethrough.

11. The storage system of claim 1 in which said horizontal and sloping tubular struts are interconnected at their places of intersection by means comprising: two annular flanges each having a central opening therein and attached respectively to the ends of a pair of opposing horizontal tubular struts: an interconnecting member comprising two vertically disposed main plates attached respectively to said flanges, each having an opening in registry with said flange openings, said main plates being rigidly attached to each other by a pair of cross plates passing through, secured to, and positioned parallel to the axis of a sloping tubular strut located between the opposing horizontal struts, said sloping struts including openings opposite the respective flange and main plate openings, thereby permitting communication between the interiors of the sloping strut and both horizontal struts.

12. A movable ballastable foundation base for a submerged liquid storage system adapted to be floated to a selected offshore site and there positioned on the floor of a body of water and to support a tank enclosure on its upper surface, comprising a hollow vessel for containing ballast material having rigid bottom wall, side wall and roof members providing a platform, an upwardly extending tapering rigid hollow shaft integrally mounted in the central portion of said roof memher and therethrough in communication with the interior of the hollow vessel, means located at the top of said shaft for introducing or removing ballast or other material into or out of the interior of said vessel, exit means for removal of air displaced from said vessel by said ballast, said shaft having means at its upper portion to support and interlock with the upper end of said tank enclosure, and said vessel including an annular peripheral segment adapted to support the lower end of said tank enclosure, when the enclosure is superimposed on said platform.

13. Method for installing an underground liquid storage system at a selected off-shore site, said system comprising a foundation base adapted to be positioned on the floor underlying a body of water and having a ballastable hollow platform having integrally mounted in the central portion thereof an upwardly extending tapering hollow shaftin communication with said platform and adapted to support and interlock therewith a tank enclosure, a rigid tank enclosure removably mountable on the exterior of said shaft, said enclosure comprising a rigid framework assembly of a plurality of interconnecting and communicating horizontal and upwardly sloping rigid tubular struts providing the configuration of a surface of revolution and a web of flexible elastomeric material surrounding the exterior of and mounted upon the framework, comprising the steps of:

a. erecting said foundation base, including the hollow shaft, on shore, launching said base into a body of water and towing the base afloat to a point above said site;

b. introducing air under pressure into said hollow shaft to maintain buoyancy of the base during ensuing base submergence onto said site;

c. filling or ballasting said foundation base as required;

d. erecting said tank enclosure framework and applying said web of flexible elastomeric material to the exterior of said framework afloat above said foundation base by successive upward assembly of the horizontal and sloping strut systems while simultaneously maintaining the buoyancy thereof; and

e. lowering said completed enclosure framework including said web of elastomeric material thereon onto the submerged foundation base.

UNITED STATES PATENT OFFICE CE I OF CORRECTION" Patent 5,805,855 Dated April 16, 1974 Inventor(s) A1 101! S Melkiel I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column-.4, line 1 1, "25" should reed 's-5' Slihe 45, "fouda' should read -founda- Column 9, lirie 9', "folly" should read --full--;

10th line from bottom, "of" should read --is--' I Signed and sealed ,thie 24th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents FOR M Po-wso (10-69) USCOMWDC 603764,

' I i ".S. GOVIRNMINT 'FUNTING OPTIC! Z I." 0"I',l 

1. A submerged liquid storage system adapted for off-shore use, comprising in combination: a. a foundation base adapted to be positioned on the floor underlying a body of water, comprising a ballastable hollow platform having integrally mounted in the central portion thereof an upwardly extending tapering hollow shaft in communication with said hollow platform adapted to support and interlock therewith a tank enclosure at the upper portion of said shaft; b. a rigid tank enclosure framework removably mounted on the exterior of said shaft, comprising an assembly of a plurality of interconnecting and communicating horizontal and upwardly sloping rigid tubular struts, said sloping struts diverging toward the lower end of the assembly to provide the configuration of a surface of revolution; c. a plurality of individual panels of a web of flexible elastomeric material forming an envelope surrounding the exterior of said rigid framework and mounted thereon to provide an outer tank wall, and defining, in combination with the outer surface of said shaft, a hollow storage space; d. means located on the upper surface of said foundation base for separably supporting the lower end of said tank enclosure framework; and e. means for introducing or removing liquid located at the upper portion of said tank enclosure and communicating with the storage space formed by said enclosure and the shaft.
 2. The storage system of claim 1 in which said foundation base shaft includes a frusto conical lower portion merging into a cylindrical upper portion, said lower portion communicating with the interior of said platform.
 3. The storage system of claim 1 in which said foundation base includes a peripheral downwardly extending cutting edge member adapted to penetrate said floor when the foundation base is ballasted and thereby anchor the storage system and prevent drifting.
 4. The storage system of claim 1 in which said platform includes a peripheral inclined annular member adapted to support the lower ends of said sloping tubular struts of said tank enclosure seated thereon.
 5. The storage system of claim 1 in which said tank enclosure and its upwardly sloping supporting strut system is generally conical in configuration.
 6. The storage system of claim 1 in which said struts are braced at their points of intersection by a plurality of radially disposed bracing members extending inwardly and connected to an annular girder member engaging the outer surface of said shaft, the respective girder members for each strut set having a diameter corresponding to the configuration of shaft at the level of the set.
 7. The storage system of claim 1 in which said tank enclosure includes at its upper end a hollow vessel communicating with the interior of the enclosure and having inlet or discharge means in its roof for receiving or removing materials, and being removably connected with the upper end of said strut framework to form an airlock and a seal with the upper end of said envelope.
 8. The storage system of claim 1 in which the upper ends of said sloping tubular struts are fastened to the upper portion of said shaft thereby interlocking said tank enclosure to the foundation base.
 9. The storage system of claim 1 in which said tank enclosure further includes an outer protective structure located exteriorly of said elastomeriC material and fastened to said framework comprising a plurality of spaced buffer members capable of resisting and reducing wave forces.
 10. The storage system of claim 1 in which said sloping tubular struts are provided with vent means located adjacent the upper and lower end of the strut to permit passage of air or liquid therethrough.
 11. The storage system of claim 1 in which said horizontal and sloping tubular struts are interconnected at their places of intersection by means comprising: two annular flanges each having a central opening therein and attached respectively to the ends of a pair of opposing horizontal tubular struts: an interconnecting member comprising two vertically disposed main plates attached respectively to said flanges, each having an opening in registry with said flange openings, said main plates being rigidly attached to each other by a pair of cross plates passing through, secured to, and positioned parallel to the axis of a sloping tubular strut located between the opposing horizontal struts, said sloping struts including openings opposite the respective flange and main plate openings, thereby permitting communication between the interiors of the sloping strut and both horizontal struts.
 12. A movable ballastable foundation base for a submerged liquid storage system adapted to be floated to a selected offshore site and there positioned on the floor of a body of water and to support a tank enclosure on its upper surface, comprising a hollow vessel for containing ballast material having rigid bottom wall, side wall and roof members providing a platform, an upwardly extending tapering rigid hollow shaft integrally mounted in the central portion of said roof member and therethrough in communication with the interior of the hollow vessel, means located at the top of said shaft for introducing or removing ballast or other material into or out of the interior of said vessel, exit means for removal of air displaced from said vessel by said ballast, said shaft having means at its upper portion to support and interlock with the upper end of said tank enclosure, and said vessel including an annular peripheral segment adapted to support the lower end of said tank enclosure, when the enclosure is superimposed on said platform.
 13. Method for installing an underground liquid storage system at a selected off-shore site, said system comprising a foundation base adapted to be positioned on the floor underlying a body of water and having a ballastable hollow platform having integrally mounted in the central portion thereof an upwardly extending tapering hollow shaft in communication with said platform and adapted to support and interlock therewith a tank enclosure, a rigid tank enclosure removably mountable on the exterior of said shaft, said enclosure comprising a rigid framework assembly of a plurality of interconnecting and communicating horizontal and upwardly sloping rigid tubular struts providing the configuration of a surface of revolution and a web of flexible elastomeric material surrounding the exterior of and mounted upon the framework, comprising the steps of: a. erecting said foundation base, including the hollow shaft, on shore, launching said base into a body of water and towing the base afloat to a point above said site; b. introducing air under pressure into said hollow shaft to maintain buoyancy of the base during ensuing base submergence onto said site; c. filling or ballasting said foundation base as required; d. erecting said tank enclosure framework and applying said web of flexible elastomeric material to the exterior of said framework afloat above said foundation base by successive upward assembly of the horizontal and sloping strut systems while simultaneously maintaining the buoyancy thereof; and e. lowering said completed enclosure framework including said web of elastomeric material thereon onto the submerged foundation base. 